1. Field of the Invention
The present invention relates to a structure and method for electrically connecting a plurality of bus bars of an electric circuit to a printed circuit board, on which a control circuit is mounted, in an electric connection box mounted on a vehicle.
2. Description of the Related Art
Generally, in a junction box to be mounted on a vehicle, an electric circuit is constituted by many bus bars formed by being punched out from metallic plates. Further, in recent years, there has been provided a junction box having a printed circuit board on which a control circuit is mounted so as to add advanced control functions to the electric circuit. In the case of such circuits, there is the necessity for electrically connecting the bus bars to the printed circuit board. For example, JP-A-2000-22353 Official Gazette discloses tab terminals, which are formed by bending end portions of the bus bars in such a way as to extend upright and inserted into through holes provided in the printed circuit board and electrically connected to the circuit mounted on the substrate by soldering, as means therefor.
FIGS. 11 and 12 illustrate a practical structure thereof. A bus bar board 2 illustrated in FIG. 11 comprises a plurality of insulating plates 3, and bus bar layers each consisting of a plurality of bus bars 4. In this board, the plurality of insulating plates 3, and the bus bar layers are alternately stacked. End portions of appropriate ones of the bus bars 4 are turned upwardly, as illustrated in FIG. 12. Thus, tab terminals 4a projecting upwardly are formed.
On the other hand, predetermined electronic circuit components 5a are mounted on a printed circuit board 5. Further, a plurality of through holes 5b are provided in the printed circuit board 5. Inner surfaces of these through holes 5b are plated with a metallic material. The plated portions thereof are electrically connected to a printed circuit. Moreover, each of the tab terminals 4a is inserted into a corresponding one of the through holes 5b and soldered to the circuit. Thus, the terminals 4a corresponding to the end portions are electrically connected to a control circuit provided on the printed circuit board 5 through the portions plated with the metallic material.
A connecting structure, in which the tab terminals 4a turned upwardly from the bus bars are inserted into the through holes 5b of the printed circuit board 5, as described in the aforementioned Official Gazette, has the following problems to be solved.
A) The plurality of bus bars 4 are formed by punching a single metallic plate into a predetermined shape. However, when the tab terminals 4a are turned upwardly, there is the need for punching the metallic plate into a predetermined shape including that of each of the tab terminals 4a. Therefore, the area of the metallic original plate increases by the area of the developed tab terminals 4a. Thus, the final area of the board increases. This impedes the miniaturization of the circuit.
B) It is necessary for connecting the bus bar board 2 to the printed circuit board 5 that each of the tab terminals 4a is accurately aligned with a corresponding one of the through holes 5b. However, the step of turning the tab terminals 4a upwardly from the bus bars 4 is not easy to perform. It is difficult to accurately align each of the positions, at which the tab terminals are turned upwardly, with a corresponding one of the positions of the through holes 5b. Especially, in the case that many tab terminals 4a and many through holes 5b are provided therein, it is very difficult to accurately align all the tab terminals 4a with the through holes 5b. Even when all the tab terminals 4a could be accurately aligned with the through holes 5b, an operation of connecting the tab terminals 4a to the through holes 5b is very troublesome. Moreover, each of the tab terminals 4a is relatively short and possesses high stiffness. This makes it very difficult to connect the tab terminals 4a to the circuit board 5 when the positions, at which the tab terminals 4a are actually formed, are deviated from the correct positions thereof. Thus, the conventional structure has the problem that it is very difficult to achieve the alignment between the tab terminals 4a and the through holes 5b. 
C) The tab terminals 4a are connected to the printed circuit board 5 only by soldering. Thus, the connecting strength therebetween is low. Consequently, it is difficult to maintain the connection between the tab terminal 4a and the printed circuit board 5 in a favorable condition against an external force.
Accordingly, in view of such circumstances, an object of the present invention is to provide a structure and method, which can highly reliably connect bus bars to a printed circuit board by using a simple configuration and performing a simple process without increasing the occupied area of the bus bars.
To achieve the foregoing object, according to an aspect of the present invention, there is provided a circuit board connecting terminal assembly (hereunder referred to simply as a first terminal assembly) for electrically connecting a plurality of bus bars, which constitute an electric circuit, to a printed circuit board, on which a control circuit is mounted. This terminal assembly comprises a plurality of board connecting terminals, each of which has a board connecting portion formed at an end thereof and electrically connected to the printed circuit board by being inserted into a through hole provided in the printed circuit board and also has a pressed-in portion to be press-fitted into a press-fitting hole formed in each of the bus bars by being elastically deformed. These board connecting terminals are fixed to a common insulating connecting element, so that the pressed-in portions of the board connecting terminals face to the same side, that the board connecting portions face, and that the board connecting terminals are formed in such a way as to be arranged in parallel with one another and as to be integral with one another.
When this circuit board connecting terminal assembly is used, a plurality of bus bars and a printed circuit board can easily be connected to one another by performing a method (hereunder referred to as a first method) including the following steps.
That is, first, the first method comprises the step of preliminarily manufacturing the circuit board connecting assembly. In the case that an embodiment (hereunder referred to as a second method) of the first method includes, for example, the step of molding an insulating connecting element around the plurality of board connecting terminals arranged in parallel with one another as a practical process for preliminarily manufacturing the assembly, the second method excels in mass-productivity. The circuit board connecting terminal assembly (hereunder referred to as a second terminal assembly) manufactured in this way, that is, a molding product obtained by molding the insulating connecting element around the plurality of board connecting terminals arranged in parallel with one another excels in strength, because each of the board connecting terminals is firmly fixed to the insulating connecting element.
The first method further comprises the step of attaching the assembly to the printed circuit board. That is, the board connecting portions of the board connecting terminals of the terminal assembly are inserted into the through holes and then connected and fixed to the printed circuit board. At this step, a printed circuit board (hereunder referred to as a first printed circuit board) with board connecting terminals are produced in such a way as to comprise a circuit board terminal assembly, and a printed circuit board having a control circuit mounted thereon and a plurality of through holes provided therein so that each of board connecting portions of board connecting terminals of the terminal assembly is electrically connected to the printed circuit board by being inserted into a corresponding one of the plurality of through holes. In this printed circuit board, the board connecting terminals of the circuit board connecting terminal assembly are fixed thereto by being bound thereto by an insulating connecting element. Thus, the fixed state thereof is stable. Further, the printed circuit board excels in strength. Moreover, the connection between the printed circuit board and each of the board connecting terminals is maintained in a stable state and highly reliable. Therefore, the following step of press-fitting pressed-in portions into press-fitting holes is performed without strength problem.
Especially, in the case of an embodiment (hereunder referred to as a second printed circuit board) of the first printed circuit board, the board connecting portions of the board connecting terminals are inserted into the through holes provided in the printed circuit board to a position at which the connecting portions are placed when the insulating connecting element of the circuit board connecting terminal assembly touches a surface of the printed circuit board. In this case, the fixed state is more stable with higher reliability of the connection between the printed circuit board and each of the board connecting terminals.
The first method further comprises the step of forming the press-fitting holes and the step of fitting the pressed-in portions into the press-fitting holes. That is, the press-fitting holes are formed in the bus bars, respectively. Then, the pressed-in portions of the board connecting terminals are press-fitted into the press-fitting holes and electrically connected to the bus bars, respectively. The electrical connection between the printed circuit board and each of the bus bars can easily be performed by such a press-fitting operation.
According to the connecting method comprising the aforementioned steps, the circuit board connecting terminal assembly is first manufactured. Then, the board connecting portion of each of the board connecting terminals is inserted into a corresponding one of the through holes formed in the printed circuit board and fixed thereto. Subsequently, the pressed-in portion at the opposite side of each of the terminals is press-fitted into a corresponding one of the press-fitting holes formed in the bus bars. Thus, as compared with the case of the conventional structure, in which the tab terminals of the bus bars are directly inserted into the through holes formed in the printed circuit board, the alignment between the tab terminals and the through holes is easier to perform in the case of a structure obtained according to the invention. Moreover, halfway through the manufacture of the structure, the electrical connection between the printed circuit board and each of the board connecting portions can be maintained in a favorable condition by the insulating connecting element connecting the terminals in such a manner as to be bound to one another.
Further, according to the circuit board connecting structure (hereunder referred to as the first structure) obtained in this manner, the electrical contact between the pressed-in portions and the bus bars are reliably maintained by elastic forces of the pressed-in portions.
Especially, in the case of an embodiment (hereunder referred to as a second structure) of the first structure, the press-fitting holes of the bus bars are formed by partly bending the press-fitting holes of the bus bars in a direction, in which the pressed-in portions are inserted, and constituted so that the pressed-in portions are pressure-contacted onto the surfaces of the bent parts of the pressed-in portions, the second structure gains the depth of the press-fitting holes by forming the bent parts even when the thickness of each of the bus bars is small. Thus, the electrical contact between the inside surfaces (that is, the surfaces of the bent parts) of the press-fitting holes and the pressed-in portions of the board connecting terminals is stably maintained.